Delivery system for generating liquid active materials using an electromechanical transducer

ABSTRACT

A delivery system and methods for generating droplets of liquid active materials, such as a perfume, air freshener, insecticide formulation, and volatile materials, to the atmosphere by means of a electromechanical transducer. The electromechanical transducer employs a first period of activation and a second period of deactivation to increase the distribution of volatile materials contained within the liquid active materials to the atmosphere and reduce the hedonic habituation of the user. The electromechanical transducer is configured to improve flow rate and decrease deposition of the droplets on to nearby surfaces.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/846,598, filed Sep. 22, 2006.

FIELD OF THE INVENTION

The present invention relates to a delivery system for generating liquidactive materials, such as perfumes, air fresheners, insecticideformulations, and volatile materials, to the atmosphere by means of anelectromechanical transducer.

BACKGROUND OF THE INVENTION

A number of processes exist for the generation of liquid droplets usingelectromechanical actuation. One method for such distribution is toatomize a liquid by a delivery system comprising a perforate structurewhich is vibrated by an electromechanical transducer which has acomposite thin-walled or planar structure, and is arranged to operate ina bending mode. Liquid is supplied to the vibrating perforate structureand sprayed therefrom in droplets upon vibration of the perforatestructure. Such attempts in the art are illustrated in U.S. Pat. Nos.3,543,122, 3,615,041, 4,479,609, 4,533,082, 4,790,479, 5,518,179,5,297,734, 6,341,732, 6,378,780, and 6,386,462.

While electromechanical transducer delivery systems are known in art,their difficulties are known as well. Specifically, there have beenefforts to improve the overall distribution of the atomized liquids in avolume of space. However, many of these delivery systems suffer becauseof their inability to properly “loft” the atomized liquids in the airhigh enough to achieve sufficient dispersion such that the distributionof the liquid active materials is maximized. Thus, a need exists for animproved delivery system and method for generating droplets of liquidactive materials to increase the distribution of the liquid activematerials beyond that which is currently capable.

SUMMARY OF THE INVENTION

The invention relates to a delivery system for generating droplets ofliquid active materials such as perfumes, other volatile liquids and/orvolatile materials including a liquid supply component comprising aliquid reservoir containing a liquid; an electromechanical transducerupon excitation by a power supply; a droplet generation elementoperatively associated with the electromechanical transducer andpositioned for contact with the liquid; and a timing mechanism foractivating said electromechanical transducer over a first period, anddeactivating said electromechanical transducer over a second period;wherein said first period is between about 20 and about 120milliseconds.

The invention also relates to a method of distributing liquid activematerials to an atmosphere comprising the steps of: providing a quantityof the liquid active materials; providing an electromechanicaltransducer in communication with the liquid active material; activatingthe electromechanical transducer to distribute the liquid activematerial to the atmosphere; and carrying out the activation for a firstperiod of time of at least about 20 milliseconds.

The invention also relates to a method of distributing liquid activematerials to an atmosphere comprising the steps of: providing a quantityof said liquid active materials; providing an electromechanicaltransducer in communication with said liquid active materials;activating said electromechanical transducer for a first period;deactivating the transducer for a second period, said first period andsecond period forming a operating cycle and repeating said operatingcycle at least once, wherein said first period is at least about 20milliseconds.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with the claims particularly pointingand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of a delivery system ofthe present invention;

FIG. 2 is a cross-sectional view of one embodiment of a delivery systemof the present invention;

FIG. 3 is an enlarged top view of one embodiment of the dropletgeneration element of the present invention;

FIG. 4 is an enlarged cross-sectional view of the droplet generationelement in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a delivery system and methods describedabove. Without wishing to be bound by theory, it is believed thatcontrolling the length of the first period and the second periodprovides a surprising increase in the distribution of the volatilematerials contained within the liquid active materials and reduction ofthe hedonic habituation of the user. By controlling the length of thefirst period of time and the second period of time, the transition orevaporation of liquid droplets to finer droplets and/or a gaseous stateas a means to increase liquid active material distribution is improved.The length of the first period controls the increased evaporation rateof the droplets of the liquid active materials, enhancing theirtransition to an atomized or molecular state and increasing theirability to remain airborne, disperse, and diffuse. In turn, thisincreases the room fill capability of the liquid active materials. Thesecond period or the deactivation period, in one aspect, is used toreduce the level of habituation by the user. Habituation is a processused by the olfactory sensory system to reduce its sensitivity to apreviously detected scent. Without wishing to be bound by theory, thesecond period of time allows for the volatile concentration of theliquid active materials to reduce below the habituation level thresholdallowing the reset of the olfactory system and the re-detection orre-perception of the scent. In effect, the first and second periodssurprisingly increase the perceived intensity of the liquid activeformulation.

Timing Mechanism

Controlling the length of the first period and second period accordingto the present invention creates chimney or “airbus” effect wherein theamount of air entrainment as well as the velocity of the dropletsincrease, resulting in an increased concentration of airborne volatilematerials from the liquid active materials as evidence by the higherdetection of components. This effect improves the perceived intensityand hedonics of the liquid active material. The timing mechanism can becontrolled by any of the known intelligent systems in the art. The firstperiod and second period, together forming an operating cycle, can berepeated at least once. In another embodiment, the operating cycle isrepeated until the liquid active material is exhausted and/or the powersupply is exhausted.

In one embodiment, the first period is at least about 5 milliseconds; inanother embodiment at least about 10 milliseconds; in another embodimentat least about 20 milliseconds; in another embodiment at least about 50milliseconds; in another embodiment at least about 100 milliseconds; inanother embodiment at least about 250 milliseconds; in anotherembodiment at least about 500 milliseconds; in another embodiment atleast about 1 second; in another embodiment at least about 5 seconds. Inanother embodiment, the first period is between about 5 milliseconds andabout 5 seconds; in another embodiment between about 10 milliseconds and1 second; in another embodiment between about 20 milliseconds and 500milliseconds; in another embodiment between about 50 milliseconds and100 milliseconds.

In one embodiment, the second period is between about 1 second and 30hours; in another embodiment between about 1 second and 24 hours; inanother embodiment between about 5 seconds and 12 hours; in anotherembodiment between about 5 seconds and 8 hours; in another embodimentbetween about 5 seconds and 6 hours; in another embodiment between about5 seconds and 4 hours; in another embodiment between about 5 seconds and3 hours; in another embodiment between about 5 seconds and about 2hours; in another embodiment between about 5 seconds and about 1 hour;in another embodiment between about 5 seconds and 45 minutes; in anotherembodiment between about 5 seconds and 30 minutes; in another embodimentbetween about 5 seconds and 20 minutes; in another embodiment betweenabout 5 seconds and 15 minutes; in another embodiment between about 5seconds and 10 minutes; in another embodiment between about 5 secondsand about 5 minutes; in another embodiment between about 5 seconds andabout 150 seconds; in another embodiment between about 20 seconds andabout 120 seconds; in another embodiment between about 25 seconds andabout 80 seconds; in another embodiment between about 10 seconds andabout 40 seconds. It is understood, however, that periods of time longerthan the above ranges of time may be utilized with the presentinvention.

Liquid Active Materials

The liquid active materials of the present invention include volatilematerials, nonvolatile materials, and combinations thereof. The liquidactive materials of the present invention readily flow at temperaturesof between about 10° C. and about 30° C. The liquid active materials maybe generated in various facilities, which include but are not limited torooms, houses, hospitals, offices, theaters, buildings, and the like, orinto various vehicles such as trains, subways, automobiles, airplanes,the outdoors and the like. The volatile materials of interest herein canbe in any suitable form including, but not limited to: dispersion ofsolids, emulsions, liquids, and combinations thereof. For example, thedelivery system may contain a volatile material comprising asingle-phase composition, multi-phase composition and combinationsthereof, from one or more sources in one or more carrier materials (e.g.water, solvent, etc.).

Nonvolatile materials, including solids, are also contemplated for usewith the present invention. It is believed that when nonvolatilematerials are part of the liquid active material, the nonvolatilematerials are finely dispersed in the air into particles capable ofbeing at least partially carried by air.

It should be understood that when the droplets of liquid activematerials are described herein as being “distributed”, “generated” or“released”, this refers to the volatilization of the evaporativecomponents of the volatile materials and to the release to theatmosphere of the non-evaporative components, which may be small solidsor particulates.

The term “solids” as used herein, refers to a material that has atangible or concrete form as discrete material at room temperature (22°C.), that is, they tend to keep their form rather than flow or spreadout like liquids or gases. The solids may be dissolved in theformulation or suspended throughout. Solids may behave very similar tobase notes as they bring depth and body to a perfume. The terms“volatile materials”, “aroma”, and “scents”, as used herein, include,but are not limited to pleasant or savory smells, and, thus, alsoencompass scents that function as fragrances, deodorizers, odoreliminators, malodor counteractants, insecticides, insect repellants,medicinal substances, air fresheners, deodorants, aromacology,aromatherapy, or any other odor that acts to condition, modify, orotherwise charge the atmosphere or to modify the atmosphere.

In addition, the term “volatile materials” as used herein, refers to amaterial or a discrete unit comprised of one or more materials that isvaporizable, or comprises a material that is vaporizable without theneed of an energy source. Any suitable volatile material in any amountor form may be used. The term “volatile materials” includes but is notlimited to compositions that are comprised entirely of a single volatilematerial. It should be understood that the term “volatile material” alsorefers to compositions that have more than one volatile component, andit is not necessary for all of the component materials of the volatilematerial to be volatile. The volatile materials described herein may,thus, also have non-volatile components.

The volatile material may comprise a perfume, although the invention isnot so limited. A perfume may include a single aromatic chemical or amixture of aromatic chemicals. As used herein, aromatic chemicals meanchemicals that have an odor. There are several chemical classes whichfall within aromatic chemicals, including but not limited to ionones,hydrocarbons, alcohols, aldehydes, ketones, esters, etc.

The term “fragrance” or “perfume” refers to all organic substances whichhave a desired olfactory property and are essentially nontoxic. They canbe compounds of natural, semi synthetic or synthetic origin. A fragrancecan be a combination of various odorous substances which evaporate atdifferent rates and/or during different periods. Fragrance can exhibitwhat is known as a “top note,” which may be the odor which firstdiffuses when the fragrance is applied, generated or released to theatmosphere, a “heart note” or “middle note,” which may complete orcomplement the fragrance providing body and texture, and a “base note,”which may be the most substantive odor and can be perceived severalhours after application or emission.

In order to be noticeable, a perfume has to be volatile, its molecularweight being an important factor along with the nature of the functionalgroups and the structure of the chemical compound. Thus, most perfumeshave molecular weights of up to about 200 Dalton, with molecular weightsof 300 Dalton and higher being more the exception. In view of thedifferences in volatility of perfumes, the odor of a perfume orfragrance composed of several perfumes changes during the evaporationprocess, the odor impressions being divided into the top note, themiddle note or body and the base note.

Since odor perception is also based to a large extent on odor intensity,the top note of a perfume or fragrance may not consist solely of readilyvolatile compounds. The base note may consist largely of less volatile,i.e. firmly adhering, perfumes. In the composition of perfumes, morereadily volatile perfumes may be fixed, for example, to certain“fixatives”, which prevents them from vaporizing too rapidly. Theperfume may also contain small amounts of other additives, such assolvents, preservatives, antioxidants, UV screening agents and the like.The fragrance matrix may also include organoleptic components, such asfor example, other well-known fragrance ingredients. The fragrances orperfumes may include natural and/or synthetic oils, extracts and/oressences which may comprise complex mixtures of constituents, such asorange oil, lemon oil, rose extract, lavender, musk, patchouli, balsamessence, sandalwood oil, pine oil, and cedar oil.

A useful term to quantify the degree of volatility of the volatilematerials is the Kovat's Index. The Kovat's Index (KI, or RetentionIndex) may be defined by the selective retention of solutes or perfumeraw materials (PRMs) onto the chromatographic columns. It is primarilydetermined by the column stationary phase and the properties of solutesor PRMs. For a given column system, a PRM's polarity, molecular weight,vapor pressure, boiling point and the stationary phase propertydetermine the extent of retention. To systematically express theretention of analyte on a given GC column, a measure called Kovat'sIndex is defined. The Kovat's Index places the volatility attributes ofan analyte (or PRM) on a column in relation to the volatilitycharacteristics of n-alkane series on that column. Typical columns usedare DB-5 and DB-1.

By this definition the KI of a normal alkane may be set to 100n, wheren=number of C atoms of the n-alkane. With this definition, the Kovat'sindex of a PRM, x, eluting at time t′, between two n-alkanes with numberof carbon atoms n and N having corrected retention times t′n and t′Nrespectively will then be calculated as:

$\begin{matrix}{{KI} = {100 \times \left( {n + \frac{{\log\mspace{11mu} t_{x}^{\prime}} - {\log\mspace{11mu} t_{n}^{\prime}}}{{\log\mspace{11mu} t_{N}^{\prime}} - {\log\mspace{11mu} t_{n}^{\prime}}}} \right)}} & (1)\end{matrix}$

This equation can be used to calculate the Kovat's index for anyvolatile material. Furthermore, this equation can be used to furtherseparate volatile components into three categories; top, middle and basenotes. Using the Kovat's index, a top note may as have a KI less than orequal to 1200, a middle note between 1200 and 1400, and a base notegreater than or equal to 1400. For example, a typical perfumeformulation having 2 percent solids may comprise 70 percent top notes,20 percent middle notes, and 10 percent bottom notes. A, comparableformulation having about 3 percent solids may comprise about 40 to about60 percent, particularly about 50 percent top notes; about 20 to about40 percent, particularly about 30 percent middle notes; and about 10 toabout 30 percent, particularly about 20 percent bottom notes.

Delivery System

Now referring to FIGS. 1 and 2, a non-limiting and exemplary deliverysystem 1 is shown. The delivery system 1 includes a liquid reservoir 4,which contains a liquid active material to be atomized, that may bejuxtaposed with and mounted below the electromechanical transducer 3 anddroplet generation element 2. The liquid supply component 5 may extendupwardly from within the reservoir 4 to the rear face of the dropletgeneration element 2 or to a region in fluid communication with thedroplet generation element 2. Upon activation of the electromechanicaltransducer 3, the liquid active material is generated through thedroplet generation element 2, the orifice 10, and into the atmosphere.

The reservoir 4 may comprise any liquid tight container suitable forholding an adequate quantity of the liquid active materials to bedispensed. The reservoir 4 may be pressurized to provide for delivery ofthe liquid active materials to the droplet generation element 2, or maybe maintained at atmospheric pressure. Upon depletion of the reservoir4, the reservoir 4 may be refillable with liquid active materialprovided from a bulk supply or the reservoir 4 may be replaced with anew reservoir containing a quantity of liquid active material.

The liquid active materials may be delivered to a droplet generationelement 2 by a liquid supply component 5 working by gravity feed,capillary action, pumping action, etc. When the droplet generationelement 2 is a perforate structure, the liquid supply component 5 may bedisposed near the center of the droplet generation element 2 so that theliquid supply component 5 may contact the perforations 2 a, 2 b, 2 c ofthe droplet generation element 8. However, the liquid supply component 5need not contact the perforations 2 a, 2 b, 2 c and the perforations 2a, 2 b, 2 c may be laterally displaced from the liquid supply component5.

A continuous feed of the liquid active material from the reservoir 4 tothe droplet generation element 2 may be desired. The continuous feed maybe accomplished by a using liquid supply component 5, which may comprisea feed tube that delivers liquid active material to the rear face of thedroplet generation element 2 or to a position juxtaposed with the rearface of the droplet generation element 2. The rear face of the dropletgeneration element 2 is the face opposite from which the dropletsemerge. The liquid active materials may be delivered from the reservoir4 to one face of the droplet generation element 2 by a capillary feed.The capillary feed may be flexible and have a surface or assembly ofsurfaces over which liquid active material can pass from the reservoir 4towards the droplet generation element 2. Exemplary capillary materialforms include open cell foams, fibrous wicks, porous plastic wicks, andglass or polymeric capillary tubes.

In applications where relatively high droplet production rates and/or arelatively high percentage of solid are desired, capillary feed may beprovided by a relatively open structure, which may also be relativelyrigid. This arrangement may provide the advantage of a relatively large,unrestricted area for liquid flow for a given surface area at the wallof the capillary tube. In such a liquid transfer process the areabetween the capillary material surfaces through which liquid may flow tothe capillary surfaces, i.e., liquid volume is relatively large to thesurface area of the capillary surfaces. This geometry may provide aliquid transfer process which is less restrictive than a similartransfer process utilizing a porous capillary wick. Without being boundby theory, it is believed that an open tube capillary may minimize theinteraction between the capillary system porous media and the dispersedsolids, thereby allowing the solids to be generated with the droplets aspart of the bulk liquid with minimal liquid to solid separation. Theopen capillary tube may have a delivery rate of at least about 20, about30 or about 40 mg/hr, but is typically not more than about 80, about 70,about 60 or about 50 mg/hr.

The capillary tube may have a closed cross section, such as a circle.Alternatively, the closed cross section may be non-circular, such as anoval, square, etc. Alternatively, the open capillary tube may comprisean open channel, such as a weir, etc. The capillary tube may be rigidand made of glass, polymeric materials, etc.

Furthermore, in applications where the droplet production rates in therange of 1 mg/s or more are desired, flat channel capillaries may offerthe benefit of a relatively greater delivery rate with a simple designand ease of manufacturing. When using a flat channel designconsideration may be given to the height of the capillary, since thedrag pull on a flat capillary channel is half of that of a capillarytube, resulting in only half of the capillary rise compared to a closedtube.

If desired, plural capillary tubes may be used in parallel to transportliquid from the reservoir to the actuator. If plural capillary tubes areused, the capillary tubes may be of equal or unequal length,cross-sectional area, cross-sectional shape, length, delivery rate, etc.The capillary tubes may have a common or different origin within thereservoir. Alternatively, plural capillary tubes may be utilized todeliver a like number of plural liquids from separate reservoirs to acommon perforate structure. This arrangement provides the advantage thatincompatible materials may be kept apart, in discrete reservoirs, untilthese materials are dispensed at the point of use. The plural materialsmay be fed from their respective reservoirs to the perforate structureat the same flow rate or at different flow rates.

In yet another alternative embodiment having plural reservoirs, pluraltransducers and a like number of plural perforate structures may beutilized and operated in parallel. This arrangement provides theadvantage that no mixing of separate materials occurs until thematerials are dispensed into the atmosphere. Again, the materials may bedispensed at a common flow rate or at different flow rates. If so theplural reservoirs, transducers, perforate plates, etc. may be the sameor may differ in function and/or performance.

The delivery system 1 may comprise an electromechanical transducer 3,which is an element capable of converting electrical energy tomechanical energy. One known example of an electromechanical transducer3 comprises piezoelectric materials, which have the ability to changeshape when subject to an externally applied voltage. The voltage maycause the electromechanical transducer 3 to vibrate at certainfrequencies. The electromechanical transducer 3 may be driven with anoscillating voltage at one of the resonant frequencies of the system oralternatively with a waveform that gives droplet on demand operation.The oscillating voltage may produce a vibration in the transducer. Thevibration may, in turn, generate[s] droplets of liquid active materialthrough a droplet generation element 2, such as a perforate structurethat is operatively associated with the electromechanical transducer 3.The droplets of liquid active material are then distributed to theatmosphere. It is believed that a resultant pressure differential may beinduced in the liquid directly behind a perforate structure. Theresulting pressure differential may force the liquid through theperforations of a perforate structure to form droplets.

The electromechanical transducer 3 may comprise a piezoelectricmaterial, which vibrates at a resonant frequency under an externallyapplied voltage. The electromechanical transducer 3 may comprise variousshapes and forms, such as a round disc. A disc-shaped transducer mayhave two opposed faces. A separate electrode may be disposed on eachface and be radially poled. The electrodes may excite the length modesof the disc shaped transducer or a mode of a perforate structure.

The electrodes may be patterned so as to incorporate “drive” and “sense”electrodes. The drive and sense electrodes are electrically insulatedbut mechanically coupled through the piezoelectric transducer. A drivevoltage may be applied to the drive electrode. The resulting motion inthe transducer generates a voltage at the sense electrode. This voltagecan then be monitored and used to control the drive voltage through afeedback circuit. The electrical response may be used to adjust thevoltage to achieve specified resonances either by phase locking,amplitude maximizing or other known means. In order to maximize theelectromechanical coupling to the desired mode it may be useful to shapethe drive electrode appropriately.

The induced vibration may have an amplitude and phase induced inrelation to characteristics of the drive signal. If desired, the drivevoltage may sweep various frequencies, to provide a range of dispensingcharacteristics. Alternatively, the drive voltage may excite thetransducer at a single frequency. The single frequency may be coincidentor near the transducer's natural frequency or a harmonic thereof. Thisarrangement may provide the benefit that less power is consumed thanusing a sweep of multiple frequencies over a spectrum.

In may also be useful to incorporate a sense electrode into the deliverysystem 1. A sense electrode can give phase and amplitude informationthat allows an appropriate electronic circuit to lock on to the correctresonant mode. It may be advantageous to shape the sense electrode so asto achieve appropriate electromechanical coupling.

One embodiment of the electromechanical transducer 3 is shown in FIGS. 3and 4. In this embodiment, the electromechanical transducer 3 can have adiameter of about 10 to about 50 millimeters. In certain embodiments thediameter may be less than about 25 millimeters, less than about 20millimeters, or may be 15 about millimeters or less. Theelectromechanical transducer 3 may have a centrally located aperturetherethrough. The aperture may have a diameter of about 5 millimeters toabout 15 millimeters. The electromechanical transducer 3 may be flat andvibrate in a bending mode, expanding mode or combination thereof with amajor excursion generally perpendicular to the opposed faces of thetransducer. The bending may be bilateral or unilateral. A suitablepiezoelectric transducer is disclosed in U.S. Pat. No. 5,518,179, thedisclosure of which is incorporated by reference.

The droplet generation element 2 may be formed from a variety ofmaterials including electro formed nickel, etched silicon, stainlesssteel or plastics. The droplet generation element 2 may be flexible orstiff. A flexible design is one where the amplitudes of the vibrationalmodes of the droplet generation element 2 are large compared with thoseof the electromechanical transducer 3. The resulting motion may have asignificant effect on the droplet generation process. A stiff design isone where the amplitudes of the vibrational modes of the perforatestructure are generally equal to or smaller than those of theelectromechanical transducer. This motion generally follows the motionof the electromechanical transducer. In either design, the flexibilitymay be controlled by a choice of material and thickness. The benefit ofthe stiff design is that a stiff droplet generation element may generateuniform droplets across its surface without dampening the overall motionof the droplet generation element.

The droplet generation element 2 is operatively associated with theelectromechanical transducer 3. “Operatively associated” means that thedroplet generation element is responsive to the activation of theelectromechanical transducer 3 such that the liquid active materialpasses through the droplet generation element 2 for diffusion into theatmosphere. In one embodiment, the droplet generation element 2 isoperatively associated with the electromechanical transducer 3 by beingjoined or coupled to one face of the electromechanical transducer 3 byadhesive, solder, etc. A non-limiting, exemplary coupledelectromechanical transducer 3 is shown in FIG. 4. The dropletgeneration element 2 may also be de-coupled from the electromechanicaltransducer 3, yet still be operatively associated with the transducer 3.A suitable de-coupled electromechanical transducer is described in WO02/068128, which is incorporated in its entirety herein.

The droplet generation element 2 may be a perforate structure, as shownin FIGS. 3 and 4, that comprises plural perforations 2 a, 2 b, 2 cdisposed on a pattern, such as a hexagonal lattice. It has been foundthat structuring the droplet generation element to maximize the flowrate of the liquid active material while minimizing deposition enhancesthe perceived intensity of the liquid active formulation.

The droplet size may be determined by varying the cross sectional areaof the exit of the perforations 2 a, 2 b, 2 c. Round perforations 2 a, 2b, 2 c may have a diameter of about 1 to about 100 microns. In oneembodiment, the diameter of the perforations 2 a, 2 b, 2 c may be lessthan about 30 microns. In another embodiment, the diameter of theperforations 2 a, 2 b, 2 c may be less than about 15 microns.Alternatively, the diameter of the perforations 2 a, 2 b, 2 c may bebetween about 2 to about 10 microns. Alternatively, the diameter of theperforations 2 a, 2 b, 2 c may be between about 4 to about 8 microns.Alternatively, the diameter of the perforations 2 a, 2 b, 2 c may bebetween about 5 to about 7 microns.

The perforations 2 a, 2 b, 2 c may be tapered to have a reduction incross-sectional area in the flow direction. If a perforate structurehaving perforations 2 a, 2 b, 2 c of variable cross section is selected,the cross sectional area of the perforations 2 a, 2 b, 2 c may decreasefrom the rear face to the front face of the perforate structure. Such atapered perforation may reduce the amplitude of vibration of theperforate structure which is necessary in order to produce droplets of agiven size, due to the reduction of viscous drag upon the liquid as itpasses through such perforations 2 a, 2 b, 2 c. Consequently, arelatively lower excitation of the electromechanical transducer 3 may beused, thereby providing improved efficiency in creating the droplets tobe dispensed. In the case of a coupled electromechanical transducer andperforate structure, the relatively lesser excitation may enable the useof a relatively thick and robust perforate structure from whichsatisfactory droplet production can be achieved. This may also providethe successful creation of droplets from liquids of relatively highviscosity and may reduce the mechanical stresses in the perforatestructure. In the case of a decoupled electromechanical transducer andperforate structure, the reduction of viscous drag will also result inimproved efficiency with respect to the power that is necessary togenerate the droplets.

The droplet generation element 2 may also be a non-perforate structure.For example, the liquid active material is fed onto a face of thedroplet generation element 2 that is opposite the rear face. Dropletsare generated by vibration of the droplet generation element 2 whetherit is bending, expanding, bilateral or unilateral.

The delivery system 1 may have a first, disposable part, comprising theliquid and its container or liquid reservoir 4. The second part, may bereusable, and may comprise the electromechanical transducer 3, thedroplet generation element 2 with its associated drive electronics 9 anda power supply 8. This provides a system which is refillable.Alternatively, the system may be discarded upon depletion of thereservoir.

The delivery system can be operated from any suitable power supply 8.The power supply 8 may be a battery, electrical power from a walloutlet, solar photovoltaic conversion, etc.

The delivery system may further comprise an automatic switch, as isknown in the art. The automatic switch may activate or deactivate thedelivery system when a threshold amount of energy is or is not present.For example, the automatic switch may comprise a photocell. Thephotocell may cause the delivery system to shut down, when a thresholdamount of light is not present. This allows the delivery system to shutdown at night, in case people are not present during the evening. Thephotocell may shut down the either the fan, electromechanicaltransducer, or both. Alternatively, the delivery system, transducerand/or fan may be activated by, or be rendered inactive by, the presenceor absence of sound, motion, heat or other energy forms.

The delivery system 1 may further comprise an intensity controller 9 forcontrolling the amount of liquid active material that is dispensed intothe atmosphere. The delivery system 1 may also include a boostcontroller 8 for providing bursts of liquid active material beyond theamount normally dispensed from the delivery system 1. In anotherembodiment a heater may be utilized to assist in and accelerate thevolatilization of the liquid active materials.

The delivery system 1 may further comprise a light source. Suitablelight sources include but are not limited to light generating diodes(“LEDs”), incandescent sources of light including but not limited tofilament-based bulbs, and luminescent sources of light including but notlimited to electroluminescent, chemiluminescent, cathodoluminescent,triboluminescent, and photoluminscent materials. In one non-limitingembodiment the light source is one or more LEDs. The LED can be anynumber of colors including but not limited to yellow, white, red, green,blue, pink, or a combination thereof. One non-limiting example of an LEDsuitable for use with the present invention is part No. MV8305(available from Fairchild Semiconductor of South Portland, Me.).

In one non-limiting embodiment, the light is positioned on the deliverysystem 1 such the light is directed towards the reservoir 4. It may bedesigned such that the light turns on automatically when the deliverysystem 1 is turned on or designed such that the light is controlledseparately from the operation of the delivery system 1. If desired, thelight source could be connected to a timer incorporated in the deliverysystem 1 such that the light automatically turns-off after apredetermined time period. Also, if desired, the light source mayprovide a light that is varying in intensity.

The following examples are presented for illustrative purposes, and arenot intended, in any way, to limit the scope of the invention.

EXAMPLE 1

Example 1 compares the effect of the length of activation period onperceived intensity using a piezoelectric delivery system according tothe following Sensory Evaluation Method for delivery systems orapparatus.

A dedicated odor evaluation room is utilized for all sensoryevaluations. A trained odor evaluator verifies that there is not anyresidual perfume or room odor present in the room. The door(s) to theroom are closed and the delivery system or apparatus is activated by atest facilitator. Trained odor evaluators enter the odor evaluation roomand perform odor evaluations at the following time intervals: (1) 3minutes after activation (2) 6 minutes after activation (3) 12 minutesafter activation and (4) 18 minutes after activation. The sensoryevaluations are conducted at the following distances from the deliverysystem or apparatus starting at the furthest distance: (1) 0.9 meters(2) 1.8 meters and (3) 2.7 meters. Expert evaluators exit the roombetween odor evaluations and the door(s) are closed between odorevaluations. Expert evaluators provide odor intensity measurements on asensory rating scale of 0-5.

Perfume Intensity Scale:

5=very strong, i.e., extremely overpowering, permeates into nose, canalmost taste it

4=strong, i.e., very room filling, but slightly overpowering

3=moderate, i.e., room filling, odor character clearly recognizable

2=light, i.e., fills part of the room, with recognizable odor character

1=weak, i.e., diffusion is limited, odor character difficult todescribe,

0=no scent

Table 1 illustrates the improved perfume hedonic data at all distancesfrom the delivery system when the length of the activation time of theelectromechanical transducer is increased at constant delivering rate.This translates to the consumer as better perfume intensity andcharacter.

TABLE 1 Perfume intensity grade at given distance from the deliverysystem 0.9 meters 1.8 meters 2.7 meters Short Pulse 1.5 0.5 0.5 (10 ms)Medium Pulse 2.0 1.5 1.5 (15 ms) Longer Pulse 2.5 2.5 2.0 (60 ms)

A longer of activation period may deliver a higher intensity, morecomplex perfume character and a more substantive perfume presentationthan a corresponding perfume using a shorter activation period.

EXAMPLE 2

Example 2 compares the effect of pulsation times with respect to thenumber of detectable components by the following method, in situmonitoring of perfume components by GC/MS.

In this method, the testing delivery system is placed in a 100 ft³ roomwith standard room circulation. The samples are collected at 0.2, 3, 6,and 9 feet. For each time point a sample is taken at each position. Aninitial background room sample is taken. The delivery system is placedin the room and turned on. After that, samples are collected at initial,6, 12 and 18 minutes. The air samples are collected using 4 Gil AirPersonal Air Sampler pumps collecting samples for 3 minutes at 1L/minute. Samples are collected on 50 mg Tenax TA traps and desorbedusing an MPS-2 TDU into a GC/MS system. Samples are analyzed using a6890/5973 GC/MS with a DB-1 column (1 μm film thickness, 0.32 mm ID, 60m length). The data is reported with respect to the number of detectablecomponents as well as Flame Ionization Detector response (FID).

Table 2 shows a higher number of detectable components at all measureddistances from the delivery system at the 18 minute sample when longerpulsation time is used. Surprisingly, longer pulsation time producedsignificantly more detectable components even in the area directlybeside the delivery system. Similar trends are observed at the othertime measurements.

TABLE 2 Number of Detectable Components Given Distance from the Deliverysystem 0.2 feet 3 feet 6 feet 9 feet Short Pulse 7 7 6 7 (10 ms) LongPulse 22 17 14 12 (60 ms)

EXAMPLE 3

Example 3 compares the various perforation sizes of the dropletgeneration element and their effect on deposition and flow rate. Toimprove perceived intensity of the liquid active material, one maymaximize flow rate while minimizing deposition. In this example, thedelivery system provides deposition of less than about 6 μg and flow inthe range of about 30 mg/hr and greater.

Flow rates are measured as weight loss over time. The weight of thedelivery system is measured using a Mettler Toledo Excellence Xs403Sresponse 0.001 g over time and the weight difference (in mg) was dividedby the time period in hours to give a flow rate in mg/hr.

Plume height is determined by placing a delivery system into the centerof a cylindrical chamber. At the rear of the chamber, behind thedelivery system a darkened screen is provided. A ruler is positioned sothat the zero cm mark is directly in line with the top of the deliverysystem. The vertical distance of the plume reached is measured by theruler and the average plume height, in cm, is taken from fiveconsecutive sprays.

Deposition of is determined by collecting the non-volatilized orre-deposited liquid active materials on three filter papers, Whatman 40(Ashless, 18.5 cm Catalog number—1440 185). Two of filter papers areplaced under the bottom edge of the delivery system. The third filterpaper is cut to fit the top of the delivery system and placed with thehole cut out over the center of the delivery system. The delivery systemis placed in a room and run for a period of 17 to 18 hours. Filterpapers are extracted using 5 ml of a internal standard solvent solutioncontaining 11.4 mg of C14 in 250 ml of methanol. All samples areanalyzed by injecting 1 microliter onto a 6890/5973 CC/MS with a DB-1column (1 μm film thickness, 0.32 mm ID, 60 m length). Quantitativeresults are calculated by referencing to a known standard.

Droplet-size distributions are measured using an Oxford Laser VisisizerSystem. This technique uses high-speed, high-resolution digitalphotography to acquire images of the spray. The laser light is diffusedand used as a backlight (not a beam); the sample volume is approximately1 mm3. These images are then analyzed by the Visisizer software to yielda droplet size distribution. The measured distributions appear rougherthan distributions measured with other techniques (such as laserdiffraction) since this method actually counts and sizes individualparticles. Relevant spray statistics are then calculated from the rawdroplet-size data. In most cases, at least 2000 droplets are used tocalculate the statistics.

Table 3 illustrates that the a perforation size of about 5 microns toabout 7 microns maximizes flow rate and minimizes deposition

TABLE 3 Activation Deactivation Perforation Droplet Plume DepositionFlow Rate period (ms) period (ms) Size (μm) size (μm) height (cm) (μg)(mg/hr) 15 10 4.5 6.5 7 6 10 45 10 8 11.80 10 X 42 60 2.5 4.5 7.40 8 335 60 5 5.6 7.84 9 4 34 60 10 7 11.00 10 4 32 60 10 8 11.90 11 12 45 7510 8 12.30 12.5 13 47 100 2.5 4.5 6.70 9.5 3 33

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this written document conflicts with any meaningor definition of the term in a document incorporated by reference, themeaning or definition assigned to the term in this written documentshall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A delivery system for generating droplets of liquid active materialcomprising: a) a liquid reservoir, wherein the liquid reservoir containsa liquid active material; b) an electromechanical transducer, saidelectromechanical transducer vibrates upon excitation by a power supply;c) a droplet generation element operatively associated with saidelectromechanical transducer and positioned for contact with said liquidactive material, said droplet generation element defines a plurality ofperforations, said perforations having a diameter of about 5 microns toabout 7 microns; d) a timing mechanism for activating saidelectromechanical transducer over a first period, and alternatinglydeactivating said electromechanical transducer over a second period;wherein first period is between about 50 milliseconds and 120milliseconds; and wherein the delivery system has a deposition rate ofless than about 6 μg and a flow rate of about 30 mg/hr or greater.
 2. Adelivery system according to claim 1 wherein first period is betweenabout 50 milliseconds and 100 milliseconds.
 3. A delivery systemaccording to claim 1 wherein first period is between about 60milliseconds and 80 milliseconds.
 4. A delivery system according toclaim 1 wherein second period is between about 25 milliseconds and 80milliseconds.
 5. A delivery system according to claim 1 wherein secondperiod is between about 10 milliseconds and 40 milliseconds.
 6. Adelivery system according to claim 1 wherein said timing mechanismsubstantially continuously activates said electromechanical transducerduring said first time period.
 7. A delivery system according to claim 1wherein said timing mechanism substantially continuously deactivatessaid electromechanical transducer during said second time period.
 8. Adelivery system according to claim 1 wherein at least one of said firsttime period and said second time period can be adjusted by a user.
 9. Adelivery system according to claim 1 wherein at least one of said firsttime period can be activated on demand by the user.
 10. A deliverysystem according to claim 1 wherein said electromechanical transducer iscoupled to said droplet generation element.
 11. A delivery systemaccording to claim 1 wherein said electromechanical transducer isdecoupled from said droplet generation element.
 12. A delivery systemaccording to claim 1 wherein said delivery system further comprises anorifice and wherein said delivery system generates said liquid activematerial into the atmosphere at about 8 cm from said orifice.
 13. Amethod of distributing a liquid active material to an atmosphere, saidmethod comprising the steps of: (a) using a delivery system forgenerating droplets comprising: a liquid reservoir, wherein the liquidreservoir contains a quantity of liquid active material, anelectromechanical transducer in communication with said liquid activematerial, a droplet generation element operatively associated with saidelectromechanical transducer and positioned for contact with said liquidactive material, said droplet generation element defines a plurality ofperforations, said perforations having a diameter of about 5 microns toabout 7 microns, wherein the delivery system has a deposition of lessthan about 6 μg and a flow rate of about 30 mg/hr or greater; (b)activating said electromechanical transducer to distribute said liquidactive material to said atmosphere; and (c) carrying out said activationfor a first period of time of at least about 50 milliseconds.
 14. Amethod according to claim 13 further comprising providing a quantity ofa second liquid: (a) using an electromechanical transducer incommunication with said second liquid; (b) activating saidelectromechanical transducer to distribute said second liquid to saidatmosphere; and carrying out said activation for an alternate period oftime of at least about 20 milliseconds.
 15. A method according to claim13 wherein said liquid active material is distributed to said atmospherefor said first period of time and said second liquid is distributed tosaid atmosphere for said alternate period, said first period and saidalternate period being different.
 16. A method according to claim 13further comprising using a perforate structure wherein saidelectromechanical transducer is coupled to said perforate structure. 17.A method according to claim 13 further comprising using a perforatestructure wherein said electromechanical transducer is decoupled fromsaid perforate structure.
 18. A method according to claim 13 furthercomprising using an orifice through which said liquid active material isgenerated, wherein said liquid active material is generated into saidatmosphere at a height of about 8 cm from said orifice.
 19. A method ofdistributing a liquid to an atmosphere, said method comprising the stepsof: (a) providing a delivery system for generating droplets comprising:a liquid reservoir, wherein the liquid reservoir contains a quantity ofliquid, an electromechanical transducer in communication with saidliquid, a droplet generation element operatively associated with saidelectromechanical transducer and positioned for contact with saidliquid, said droplet generation element defines a plurality ofperforations, said perforations having a diameter of about 5 microns toabout 7 microns, wherein the delivery system has a deposition of lessthan about 6 μg and a flow rate of about 30 mg/hr or greater; (b)activating said electromechanical transducer to distribute said liquidto the atmosphere for a first period, said first period is at leastabout 50 milliseconds; (c) deactivating the transducer for a secondperiod, said first period and said second period forming an operatingcycle; and (d) repeating said operating cycle at least once.
 20. Amethod of distributing a liquid active material to an atmosphere, saidmethod comprising the steps of: (a) using a delivery system forgenerating droplets comprising: a liquid reservoir, wherein the liquidreservoir contains a quantity of liquid active material, a disc-shapedelectromechanical transducer having two opposed faces, a drive electrodedisposed on one face and a sense electrode disposed on the oppositeface, wherein said disc-shaped electromechanical transducer is incommunication with said liquid active material, a droplet generationelement operatively associated with said disc-shaped electromechanicaltransducer and positioned for contact with said liquid active material,said droplet generation element defines a plurality of perforations,said perforations having a diameter of 4.5 microns, wherein the deliverysystem has a deposition of less than about 6 μg and a flow rate of about30 mg/hr or greater; (b) activating said disc-shaped electromechanicaltransducer to distribute said liquid active material to said atmosphereusing said drive electrode and sense electrode; and (c) carrying outsaid activation for a first period of time of at least about 60milliseconds.